Repopulated retinal microglia promote Müller glia reprogramming and preserve visual function in retinal degenerative mice

Abstract

Rationale: Müller glia (MG) play a key role in maintaining homeostasis of the retinal microenvironment. In zebrafish, MG reprogram into retinal progenitors and repair the injured retina, while this MG regenerative capability is suppressed in mammals. It has been revealed that microglia in zebrafish contribute to MG reprogramming, whereas those in mammals are over-activated during retinal injury or degeneration, causing chronic inflammation, acceleration of photoreceptor apoptosis, and gliosis of MG. Therefore, how to modulate the phenotype of microglia to enhance MG reprogramming rather than gliosis is critical. Methods: PLX3397, a colony-stimulating factor 1 receptor inhibitor, was applied to deplete microglia in the retinas of retinal degeneration 10 (rd10) mice, and withdrawal of PLX3397 was used to induce the repopulated microglia (Rep-MiG). The protective roles of the Rep-MiG on the degenerative retina were assessed using a light/dark transition test, and scotopic electroretinogram recordings. Immunofluorescence, western blot, transcriptomic sequencing, and bioinformatics analysis were performed to investigate the effects and mechanisms of microglia on MG reprogramming. Results: Following PLX3397 withdrawal, Rep-MiG replenished the entire retina with a ramified morphology and significantly improved the retinal outer nuclear layer structure, the electroretinography response, and the visual behavior of rd10 mice. Coincidentally, MG were activated, de-differentiated, and showed properties of retina progenitors in a spatial correlation with Rep-MiG. Morphological and transcriptomic analyses revealed Rep-MiG significantly enhanced protease inhibitor activity and suppressed extracellular matrix (ECM) levels during retinal degeneration. Conclusions: It suggested that Rep-MiG with the homeostasis characteristic stimulated the progenitor cell-like properties of MG, probably through regulating ECM remodeling, which protected photoreceptors and improved visual function of rd10 mice. It might be a potential protocol to reprogram MG and delay mammal retinal degeneration.

Human Amniotic Epithelial Cells Promote Chx10−/Pax6+Müller Glia Subpopulation Reprogramming into Photoreceptor-like Cells

“…Thus, we investigated whether transplanted hAECs degrade inhibitory ECM components via secreting Mmp2 and Mmp9 to induce retinal regeneration. Consistent with our findings, ECM components, including CSPGs and collagen Ι, were deposited in the degenerative retina (Figure 5a-d) 42 . Almost no CSPGs were found in the retinas of C57 mice, whereas a clear CSPG band was deposited in the ONL and the external limiting membrane (ELM) (Figure 5a, b).…”

“…Excessive deposition of ECM components such as chondroitin sulfate proteoglycans (CSPGs) is frequently associated with CNS damage, including RD, which is a critical barrier to neuronal repair and regeneration 42–45 . On the one hand, GO and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the top 200 genes in hAECs showed that pathways related to ECM regulation including regulation of cell-substrate adhesion, collagen metabolic process, regulation of peptidase activity and ECM-receptor interaction were enriched (Figure S9a, b) 46 ; on the other hand, hAECs with high Mmp2 and Mmp9 expression degrade ECM components during parturition 47 .…”

“…Besides, hAECs played an important role in regulating the immune microenvironment and transplanted of hAECs significantly rescued the neuronal death through immunomodulation 79–81 . It is noteworthy that regulation of microglia-mediated neuroinflammation and other inflammatory cytokines also facilitated MG reprogram into retinal progenitors in mice 42 . It revealed that the other potential mechanism of hAECs besides ECM remodeling promoted MG reprogramming.…”

“…Glast-CreERT C57BL/6J mice were purchased from the Jackson Laboratory (cat # 012586; Bar Habor, ME, USA) and crossed with H11-tdTomato C57BL/6J mice (H11 em1Cin(CAG-LoxP-ZsGreen-Stop-LoxP -tdTomato) ) to generate Glast-CreERT/H11-tdTomato mice. We then generated MG lineage-tracing mice with a RD phenotype by crossing Glast-CreERT/H11-tdTomato mice with rd10 mice 42 . All mice were raised in a specific pathogen-free room at the Animal Care Center of Southwest Hospital on a 12-h light/dark cycle and were allowed free access to water and feed.…”

“…To induce tdTomato expression, tamoxifen (Sigma-Aldrich, St. Louis, MO, USA; T5648) dissolved in corn oil was injected intraperitoneally at 120 mg/kg body weight into MG lineage-tracing mice at P21 every day for 5 days, followed by a 7-day suspension 42 .…”